1. Field of the Invention
The present invention relates to a microscope for magnifying an object, and more particularly, to a microscope that is provided with an illuminating optical system for illuminating the object.
2. Description of the Related Art
A surgical microscope is used for magnifying minute tissues such as brain cells during surgery.
Since it is difficult to distinguish minute tissues of an intricate organ such as a brain by the naked eye, the surgical microscope is required to proceed surgery on such an organ.
Besides an observing optical system or an image taking optical system, the surgical microscope is frequently provided with an illuminating optical system to illuminate the object.
However, the illumination light may be the stray light for the observing optical system or the image taking optical system when the illumination light leaks out from a lens barrel of the illuminating optical system. Particularly, when the illuminating optical system includes a variable power lens to vary the illuminating region according to a zoom of the observing optical system or the image taking optical system, grooves are formed on the lens barrel to follow drive pins, the illumination light tend to leak out through the grooves.
On the other hand, the illuminating optical system has to include the variable power lens to vary the illuminating region. A two-group zoom lens that is known as a simple image taking zoom lens can be used as an illuminating lens.
However, since the image taking lens has a larger number of lens elements to correct aberrations than the illuminating lens, in general, an adoption of the image taking zoom lens results high cost and heavy weight. Particularly, the illuminating lens should have small F-number at the incident side when it takes divergent light exited from the light guide fiber bundle with efficiency, which further increases a number of the lens elements.
It is therefore a first object of the present invention to provide a microscope, which is able to prevent the incidence of the illuminating light into the observing optical system or the image taking optical system.
The second object of the present invention is to provide an illuminating lens, which is able to vary the illuminating region without increasing the number of lens element.
For the first object, according to the present invention, there is provided an improved microscope, which includes:
a close-up optical system that faces an object, one side of each lens included in the close-up optical system being cut out;
at least one imaging optical system that takes object light rays passing through a region of the close-up optical system, the region being offset from the optical axis of the close-up optical system in the direction opposite to the cutout side;
an illuminating optical system that guides illumination light emitted from a light source to illuminate the object;
a first lens barrel that supports the close-up optical system;
a second lens barrel that supports the illuminating optical system, the second lens barrel being arranged in the cutout space of the close-up optical system inside the first lens barrel; and
a light shielding member attached to the second lens barrel to prevent a leak of the illumination light through grooves formed on the second lens barrel.
With this construction, since an inter-axis distance between the close-up optical system and the illuminating optical system can be kept small, the parallax becomes small, which reduces the deviation between the observation region and the illuminating region in spite of the working distance. Further, since the second lens barrel is covered by the light shielding member, the illumination light does not enter in the close-up optical system, which prevents the problem of the stray light.
The microscope may be an optical microscope used for an observation by the naked eye or a television microscope that electronically capture the image of the object. Further, the microscope may be a monocular type or a stereoscopic type that includes a pair of the imaging optical systems.
The shape of the cutout line of the close-up optical system in a plane view may be straight or curved. In particular case, the cutout portion may be a through hole. The cutout surface may be parallel to the optical axis of the close-up optical system or inclined.
The illuminating optical system may include an illuminating lens for projecting illumination light. The illuminating lens may consist of a single lens group or a plurality of lens groups. It is preferable that the illuminating lens contains a plurality of lens groups that are movable along the optical axis direction to change focal length of the illuminating lens.
The first lens barrel may include a fixed ring that is fixed to a housing of the microscope, a plurality of guide grooves being formed on the circumference of the fixed ring; a cam ring that is rotatably connected around the fixed ring, a plurality of cam grooves are formed on the circumference of the cam ring such that the cam grooves intersect obliquely with the guide grooves, respectively; and a plurality of moving lens frames that are inserted in the fixed ring with holding the lens groups, respectively.
In such a case, at least one drive pin is installed on each of the moving lens frame to penetrate the intersection between the guide groove and the cam groove, and the light shielding member is attached to the outer surface of the cam ring.
The light shielding member may be formed from metal or resin. The shape of the member may be a plate, a pipe or a sheet. The shielding member is preferably coated by anti-reflection material.
For the second object, according to the present invention, there is provided an improved illuminating lens, which includes: a first lens group of a positive refractive power, all of lenses included in the first lens group are positive lenses; and a second lens group of a negative refractive power that is located at the object side with respect to the first lens group, all of lenses included in the second lens group are negative lenses.
The first and second lens groups are movable along the optical axis direction to change degree of divergence of the illumination light projected to the object.
Since the illuminating lens has a larger allowance to the aberrations correction than an image taking lens, the above construction achieves sufficient result. That is, the illumination light uniformly illuminates the object through the illuminating lens.
With this construction, the number of lens elements can be reduced as compared with the two-group image taking zoom lens.
The first lens group may include at least two positive lenses. More preferably, the first lens group may consist of three positive lenses.
Since the positive refractive power of the first lens group is distributed among a plurality of positive lenses, the spherical aberration can be reduced, keeping uniformity of the illuminance distribution with the small F-number.
The second lens group preferably consists of a single negative lens to reduce the size and weight of the illuminating lens.